The figure shows a container made up of 3 sections. Cuboid K with a square base of side 4 cm and height 35 cm. Cube L with a side of 12 cm. Cuboid M that is 73 cm by 20 cm by 48 cm. Water from a tap above flows down at a rate of 2.5 litres per minute while water is drained out from the bottom at a rate of 2 litre per minute. How long did it take to fill up the container to a height of 67 cm from the base? Give the answer in minutes correct to nearest whole number.
Volume of L
= 12 x 12 x 12
= 1728 cm³ 

Volume of M
= 73 x 20 x 48
= 70080 cm³ 

2 ℓ = 2000 cm³ 
2.5 ℓ = 2500 cm³ 

Net increase in volume per minute
= 2500 - 2000
= 500 cm³/min

Height of K to be filled with water
= 67 - (48 + 12)
= 7 cm

Volume of water in K
= 4 x 4 x 7
= 112 cm³ 

Volume of water in M, L and part of K
= 70080 + 1728 + 112
= 71920 cm³ 

Time taken to reach height
= 71920 ÷ 500
≈ 144 min (Correct to nearest whole number)

Answer(s): 144 min